KABUL — The challenger in Afghanistan's recent election called President Hamid Karzai's victory illegal and his government a failure, saying Wednesday that the tainted administration would not be able to check corruption or fend off the Taliban.

Former Foreign Minister Abdullah Abdullah said he did not plan to personally challenge Karzai's victory in court, but would leave it up to the Afghan people to decide whether to accept Karzai as the legitimate leader for another five-year term.

The Afghan election commission proclaimed Karzai the victor of the country's tumultuous ballot on Monday after Abdullah withdrew from a runoff race he said could not be free or fair. The decision ended a political crisis two and a half months after a first round of voting in August was marred by widespread fraud.

It was widely believed that Karzai would have won the runoff vote, but Abdullah contended that he was quitting not as a concession, but because he couldn't trust the process. The Karzai-appointed election commission had rejected reforms for the runoff suggested by the U.N. and a list of conditions set forth by Abdullah's camp.

Abdullah appeared to be setting himself up as an opposition leader in a country where political parties are not strong and there has never been a vigorous political movement in opposition to the president. Karzai has repeatedly said that political parties are too divisive for war-scarred Afghanistan and described himself as an independent open to working with everyone.

U.S. officials have been anxious for a credible, legitimate government to emerge from the turbulent electoral process to serve as reliable partner against the Taliban and solidify public support for the fight against the insurgents.

Question of legitimacyAbdullah said the Afghan government under Karzai had squandered eight years of opportunity and the assistance of its Western allies by failing to stop corruption or to create a government that responds to the needs of the Afghan people.

The Afghan election commission's decision to abandon the runoff was not legal and has created a government that cannot be trusted to obey laws, Abdullah said.

"That government cannot bring legitimacy, cannot fight corruption," Abdullah said, adding that it "cannot deal with all the challenges, especially the threat of terrorism, security problems, poverty, unemployment and many others."

In Washington, the highest-ranking U.S. military officer said corruption is "endemic" in Afghanistan and must be addressed head-on, including by the arrest of officials on the take. Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said Washington will be watching to see if Karzai follows through.

"You have to rid yourself of those who are corrupt. You have to actually arrest and prosecute them," Mullen said at the National Press Club. "You have to show those visible signs."

Abdullah spoke a day after five British soldiers were killed in a shooting in southern Helmand province. Afghan authorities said the attack was carried out by an Afghan policeman who opened fire on the British troops.

"Eight years of golden opportunity we have missed," Abdullah said of the money and lives spent by international forces. He said the Karzai government's ineffectiveness has made more troops necessary to restore peace.

But Abdullah said he saw the messy election as finished and did not plan to pursue a challenge.

"The process has completed itself with that final, illegal decision," he said, referring to the commission's ruling. "I leave it to the people of Afghanistan to judge."

People close to Karzai and Abdullah have said that the two have been in talks over the last few weeks to negotiate a power-sharing agreement, but no deal has emerged.

Karzai said in his victory speech Tuesday that he would welcome anyone from the opposition into his administration, but did not make a direct appeal to Abdullah to join him.

Asked why Karzai did not mention Abdullah in his speech, a spokesman said the president no longer considers Abdullah his main opponent because he dropped out before the runoff.

"Dr. Abdullah withdrew from the process in the middle of it," Humayun Hamidzada said.

Karzai's pledgeAbdullah reiterated Wednesday that he does not want a place in Karzai's government and said he has not asked for Cabinet or ministerial positions for his allies. He said he last spoke directly with Karzai a week ago.

"In this environment, I would rather act like a pressure group," Abdullah said. Asked what recommendations he would make to clean up the government, Abdullah said he had not yet formed a specific list of demands.

Karzai pledged Tuesday to banish corruption by revising laws and strengthening a corruption investigation commission that was established a year ago, but did not get more specific about what needs to be done.

Hamidzada said the government is working on a concrete plan to combat corruption, but declined to provide details.

"He is going to continue the fight against corruption and expedite and redouble efforts," he said.

Asked about the wider allegation that the government has done little to help the Afghan people, Hamidzada said Afghans' lives have improved in measurable ways: Literacy is up and many more people are able to attend school and get medical care than when Karzai first took office.

As for security, he said it was unfair to judge Karzai in the middle of a difficult push to fend off the Taliban.

"We are in the middle of a fight, a war. We have a problem, and that's why we have more than 40 countries helping us," Hamidzada said.

He added that Karzai also plans to strengthen his roster of advisers to create a more professional Cabinet, a suggestion that the president could bring in more technocrats.

"There are a number of capable people right now, and he will strengthen his Cabinet with new people," Hamidzada said.

Abdullah said in his speech that he worried that more of the same would permanently tarnish Afghanistan.